ASP.NET AJAX integration with Office SharePoint Server 2007 and Windows SharePoint Services 3.0 has been a relatively hot topic in the developer community. Here's some interesting posts on the topic of enabling ASP.NET AJAX support in your MOSS/WSSv3 solutions.
- Integrating ASP.NET AJAX with SharePoint (by Mike Ammerlaan)
Mike walks you through what you need to do to enable ASP.NET AJAX in a SharePoint site.
- AjaxBasePart: Easy ASP.NET 2.0 AJAX Extensions 1.0 and Office SharePoint Server 2007 (by Eric Schoonover)
Eric takes Mike's post one step further and talks about how you can make use of ASP.NET AJAX within SharePoint web parts with his AjaxBasePart class. Cool stuff!